This invention relates to a planetary gear apparatus suited to be used as a differential gear apparatus for vehicles.
In general, a planetary gear apparatus of this type comprises an inner gear and a sun gear rotatably disposed with their axes aligned with the rotation axis, a plurality of planetary gears which are in engagement with the inner gear and the sun gear, and a carrier rotatably disposed with its axis aligned with the rotation axis and adapted to support the planetary gears such that the planetary gears can rotate their own axes. One of the inner gear, sun gear and carrier serves as an input member and the remaining two as an output member. That is, one of the inner gear, sun gear and carrier is driven for rotation and rotation of the remaining two is extracted as an output rotation (for example, Japanese Patent Application Laid-Open Nos. H09-112657 and H09-144844).
In the above-mentioned planetary gear apparatus according to the related art, it is demanded the torque bias ratio as a ratio of the rotation torque which is to be transmitted to the two output members is set to be large. It is, therefore, an object of the present invention to provide a planetary gear apparatus in which the torque bias ratio can be set to be large.